The present invention relates to automotive bumper systems, and more particularly relates to a tubular bumper beam having an internal energy absorber in the tubular bumper beam.
Tubular bumper beams for vehicles can kink and prematurely collapse when impacted with a xe2x80x9cpointxe2x80x9d source, such as during a front impact with a telephone pole or post. It is desirable to distribute stress to reduce this tendency to kink, as a way of providing a more predictable energy absorption curve and as a way of generally increasing an impact strength of the bumper beam. There are different ways to accomplish this. For example, some tubular beams have a xe2x80x9chat-shapedxe2x80x9d sheet metal reinforcement welded longitudinally along a center of their front surface. However, this protrudes in front of the beam, taking up space and making it more complicated to attach a polymeric energy absorber and/or front fascia to the vehicle. Another alternative is to form a foam component within the internal cavity of the tubular beam. However, this process uses expensive materials, takes time for the foam to cure, and may not provide as predictable of a result as is desired.
U.S. Pat. No. 4,856,833 (to inventor Beckman) discloses a bumper beam having an elastically deformable energy-absorbing plastic element (3-11) within a tubular case (1). The specification of Beckman is not clear as to the material of the case (1). The case (1) defines a trapezoidally-shaped cavity, and the plastic element (3-11) fits mateably into the cavity and includes xe2x80x9cbox-shaped formations 4xe2x80x9d connected together by xe2x80x9cwebs 9xe2x80x9d at midpoints (7,8) of the sides of the formations (4) (see FIG. 1, and column 2, lines 11-25). The webs (9) are aligned with a line of impact xe2x80x9cFxe2x80x9d so that sides of the xe2x80x9cbox-shaped formations 4xe2x80x9d bow and collapse as the tubular case (1) collapses. (See FIG. 2.) It is not clear from Beekman how the plastic element (3-11) is retained within the tubular case (1). It is noted in column 2, lines 27-28, that xe2x80x9cA layer of foam 12 can be applied between the impact surface 3 of the energy absorber and case 13.xe2x80x9d (See column 2, lines 27-29.) This could retain the plastic element in the tubular case. However, it is also noted that the front and rear plates (12 and 11) (i.e. the force xe2x80x9cFxe2x80x9d strikes a front of the bumper beam when the beam is in a vehicle-mounted position, such that plate 12 is a xe2x80x9cfront platexe2x80x9d) include end sections (i.e. the sections outside of the webs 9) that are several times longer than they are thick. Further, the end sections engage top and bottom angled sides of the case (1). Because the end sections are long and thin, and because they engage angled surfaces, they could not wedgingly hold the plastic element (3-11) within the tubular case (1), since it appears that they would easily and simply bend under if they were stressed. This is consistent with providing an arrangement where the plastic element intentionally collapses the sidewalls of its box-shaped areas. However, it is inconsistent with the present inventive arrangement, wherein one or more walls of the energy absorber extend horizontally completely through the energy absorber from a front wall to a rear wall of a metal tubular beam in a manner preventing premature kinking or bending of a tubular metal beam during impact. It is further inconsistent with the present inventive arrangement, wherein one or more short protruding ridges are shaved off and/or bent over as the energy absorber is press-fit and/or friction-fit into the cavity of a tubular beam, as discussed below.
Accordingly, a bumper system is desired having the aforementioned advantages and solving the aforementioned problems.
In one aspect of the present invention, a bumper system for vehicles includes a tubular beam and an energy absorber. The beam has front, rear, top, and bottom walls defining an internal cavity; with the cavity, when in a vehicle-mounted position, defining an internal horizontal first dimension between the front and rear walls. The energy absorber is longitudinally-extruded and made of a non-foam polymer with wall sections forming a honeycomb-shaped structure. The honeycomb-shaped structure includes front and rear wall sections, planar stiffening wall sections that extend horizontally continuously and completely between the front and rear wall sections, and stabilizing wall sections that extend between the planar stiffening wall sections. The stiffening wall sections include stubby protrusions on at least one of the front and rear wall sections that are aligned with the planar stiffening wall sections and that combine with the front and rear wall sections to define a second dimension that is greater than the first dimension. By this arrangement, when the energy absorber is forcibly pressed into the cavity of the tubular beam, the protrusions and stiffening wall sections are stressed and friction-fit between the front and rear walls of the tubular beam.
In another aspect of the present invention, a method of constructing a bumper system for vehicles comprises steps of providing a tubular beam with front, rear, top, and bottom walls defining an internal cavity. The cavity, when in a vehicle-mounted position, defines an internal horizontal first dimension between the front and rear walls. The method further includes providing a non-foam polymeric energy absorber with wall sections forming a honeycomb-shaped structure. The honeycomb-shaped structure includes front and rear wall sections, planar stiffening wall sections that extend horizontally continuously and completely between the front and rear wall sections, and stabilizing wall sections that extend between the planar stiffening wall sections. The stiffening wall sections include stubby protrusions on at least one of the front and rear wall sections that are aligned with the planar stiffening wall sections and that combine with the front and rear wall sections to define a second dimension that is greater than the first dimension. The method still further includes forcibly pressing the energy absorber into the cavity of the tubular beam, including stressing the protrusions and stiffening wall sections between the front and rear walls of the tubular beam.
In another aspect of the present invention, a method of constructing a bumper system for vehicles comprises steps of providing a tubular beam defining an internal cavity, the tubular beam including front and rear walls, and providing an oversized non-foam polymeric energy absorber having a body and protrusions that in combination with the body to define at least one dimension that is larger than the internal cavity so that the energy absorber cannot be easily slid into the cavity. The method still further includes forcing the energy absorber into the cavity of the tubular beam, the step of forcing including at least one of deforming the protrusions or shaving the protrusions as the energy absorber is moved into the internal cavity.
In addition to supporting the front face of the beam from kinking, an object of the present invention is to have the extruded section provide additional modulus (section moment of inertia) within the geometry (package space) of the tubular beam.